1. Field of the Invention
The present invention generally relates to a magnetic head and a magnetic storage device provided with the magnetic head, and particularly relates to a magnetic head including a spin-valve head element and a magnetic storage device provided with the magnetic head.
Recently, magnetic disk devices are required to have a higher surface recording density. To provide a magnetic head which is suitable for a magnetic disk having a surface recording density of, for example, over 5G bits/(inch).sup.2, a GMR(giant magnetoresistive) magnetic head has been developed as a next-generation magnetic head. This reproduction-only GMR magnetic head includes a spin-valve head element. The spin-valve head element utilizes a giant magnetoresistive (GMR) effect. The GMR effect changes a resistance by sensing a magnetic field and the change in the resistance is several times larger than the change caused by an AMR effect. Thus, it is possible to reproduce information recorded in a magnetic disk which has higher surface recording density.
With the GMR magnetic head having the spin-valve head element, a stronger output is required and thus a higher signal-to-noise (S/N) ratio, in order to stabilize the reproduction of the information on the magnetic disk having higher surface recording density.
2. Description of the Related Art
FIG. 1 shows a GMR magnetic head 10 of the prior art. The GMR magnetic head 10 includes a spin-valve head element 11 and electrodes 12,13 connected to each end of the spin-valve head element 11, respectively. The spin-valve head element 11 is defined as including an antiferromagnetic layer 15, a spin-valve element 16 and a backing layer 17, which are laminated in an element-layer-thickness direction, and also includes hard layers 18,19 at each end in a core-width direction. The hard layers 18,19 are magnets for controlling domains of a pin layer 20 and a free layer 22, which will be described later. The spin-valve element 16 is defined as including the pin layer 20, a non-magnetic intermediate layer 21 and the free layer 22. A direction of magnetization of the pin layer 20 is in the element-height direction and a direction of magnetization of the free layer 22 is in the core-width direction, the two directions being orthogonal. A sense current flows through the spin-valve element 16 via the electrodes 12,13. As the GMR magnetic head 10 scans a rotating magnetic disk, a magnetic field from the magnetic disk changes the direction of magnetization of the free layer 22. Thus, the relation between the direction of magnetization of the pin layer 20 and the direction of magnetization of the free layer 22 changes, and the resistance of the spin-valve element 16 is also changed. The change in the resistance of the spin-valve element 16 is detected as a change in voltage. Thus, the information recorded on the magnetic disk is reproduced.
The spin-valve element 16 has a height of hl and a core width of w1. As will be described, the height and width are set to obtain a desired stronger output.
Also, each of the surfaces 25, at each end of the spin-valve head element 11 in the core-width direction, has an area S1 (indicated as a hatched are). (Here, the hard layers 18,19 are omitted for convenience.) In other words, a connection part between the electrodes 12 or 13 and the spin-valve head element 11 has a connection area of S1.
A reproduction signal is generated when the GMR magnetic head 10 reproduces the information recorded in the magnetic disk. Generally, an output of the reproduction signal is substantially inversely proportional to the height h1 of the spin-valve head element 11 (and substantially proportional to the core width w1 of the spin-valve head element 11). Thus, the height h1 of the spin-valve head element 11 is determined to be as small as possible, considering the resistance of the element or reproduction characteristic, such as bias, and reliability. Thus, the GMR magnetic head 10 reproduces the information at a stronger output.
However, if the height h1 of the spin-valve 16 is small, the area Si of the surface 25 at each end of the spin-valve head element 11 is reduced. Thus, the contact area S1 of the connection part between the electrodes 12 of 13 and the spin-valve head element 11 is also reduced.
Next, a noise that occurs upon reproduction of the information on the magnetic disk will be discussed. The noise is a synthesis of a noise from the GMR magnetic disk, a head-noise generated at the GMR magnetic head 10 and a noise generated in a circuit of the magnetic disk device. Among the above three noises, the head-noise generated at the GMR magnetic head 10 tends to be higher, when the resistance of a path through which the sense current flows is higher.
There is a problem with head-noise in the prior magnetic head 10 since the contact area S1 of the connection part between the electrodes 12 or 13 and the spin-valve head element 11 is small, the resistance of the connection part between the electrodes 12 or 13 and the spin-valve head element 11 has a high value.
Accordingly, there is a need for a spin-valve head element having the smallest possible height which makes it possible for the GMR magnetic head to reproduce signals at a stronger output.
Also, there is a need for reduced contact area of the connection part between the electrodes and the spin-value head element, which can achieve lower resistance of the connecting part.